Influence of emotional stimuli on lower limb cutaneous reflexes during human gait

Effects of postural threat on perceptions of lower leg somatosensory stimuli during standing

Height-induced postural threat affects emotional state and standing balance behaviour during static, voluntary, and dynamic tasks. Facing a threat to balance also affects sensory and cortical processes during balance tasks. As sensory and cognitive functions are crucial in forming perceptions of movement, balance-related changes during threatening conditions might be associated with changes in conscious perceptions. Therefore, the purpose of this study was to examine the changes and potential mechanisms underlying conscious perceptions of balance-relevant information during height-induced postural threat. A combination of three experimental procedures utilized height-induced postural threat to manipulate emotional state, balance behavior, and/or conscious perceptions of balance-related stimuli. Experiment 1 assessed conscious perception of foot position during stance. During continuous antero-posterior pseudorandom support surface rotations, perceived foot movement was larger while actual foot movement did not change in the High (3.2 m, at the edge) compared to Low (1.1 m, away from edge) height conditions. Experiment 2 and 3 assessed somatosensory perceptual thresholds during upright stance. Perceptual thresholds for ankle rotations were elevated while foot sole vibrations thresholds remained unchanged in the High compared to Low condition. This study furthers our understanding of the relationship between emotional state, sensory perception, and balance performance. While threat can influence the perceived amplitude of above threshold ankle rotations, there is a reduction in the sensitivity of an ankle rotation without any change to foot sole sensitivity. These results highlight the effect of postural threat on neurophysiological and cognitive components of balance control and provide insight into balance assessment and intervention.

Emotional categorization of objects: A novel clustering approach and the effect of depression

Most everyday actions engender interactions with meaningful emotionally-laden stimuli. This study aimed to select pictures of objects as emotional stimulus of affordance to be grasped. The participant's depression trait was also assessed to examine its effect on the judgment of these pictures, and time spent in the classification was computed. Sixty-three participants joined this study. Self-Assessment-Manikin scale was used to classify pictures of the objects, and Beck Depression Inventory was applied to distribute the sample according depression trait. Cluster analysis was used in the classification of 123 objects based on valence and arousal values. Cluster results returned 102 classified pictures in three categories: pleasant (21), neutral (48) and unpleasant (33). Where cluster analysis did not agree, the picture was excluded and not used any further (21). Pleasant pictures presented the highest valence values and unpleasant pictures the lowest, and both categories returned the highest arousal level. In the middle of the valence range, the neutral category evoked the lowest arousal levels. Participants were slower to classify unpleasant pictures in valence sub-scale and faster to classify neutral pictures in arousal one. There was no effect of depression in the response time needed to score the pictures. Thus, agreement of high-performance soft clustering algorithms emerged as a good tool to classify pictures representing objects based on valence and arousal dimensions. Depression trait does not significantly affect the accuracy or time-order of emotional classification. Finally, we presented a set of emotional stimuli that can be employed to examine distinct aspects of emotion over physiology and behavior.